High temperature lubricant and process of making the same



United States atent HIGH TEMPERATURE LUBRICANT AND PROCESS OF MAKING THE SAME Drawing. Filed Aug. 16, 1956, Ser. No. 604,316

Claims. c1. zen-429.7

invention relates to high temperature lubricants. More particularly, it relates to liquid lubricants of the organopolysiloxane type which are characterized by de- 's irable lubricity at high temperatures and to the preparationl of such lubricants.

Itis well known that while many naturally occurring mineral and vegetable oils have good lubricating qualities and stability at lower temperatures, at a critical higher temperature the coeificient of friction rises sharply denoting the loss of their lubricity. It has been suggested that oils of the organopolysiloxane type be substituted for the natural oils in higher temperature uses and this has been done with some success. Many of these organopoly- 'siloxane materials are those such as one obtains from the hydrolysis or co-hydrolysis and condensation of the various substituted silanes. Lubricants of this general type are set forth, for example, in Patents 2,469,888, 2,469,890, and 2,689,859, among others, assigned to the same assignee as the present invention, and also Patent 2,599,984, the teachings of which are included herein by reference.

Fluid organopolysiloxanes which have been found to he very useful as a lubricant at temperatures up to 400 F. are the hydrolysis and condensation products of chlorophenyl silanes or mixtures of such silanes containing from one to five chlorine atoms per phenyl group with alkyl silanes. A typical mixture of such silanes comprises tetrajchlorophenyltrichlorosilane, dimethyldichlorosilane and 'trime'thylchlorosilane. The product secured from the above-mentioned silanes is capable of serving as an efficient lubricant under varying loads at temperatures up to about 400 F. However, with further rise in temperature the coeflieient of friction rises sharply rendering the material of limited, if any, usefulness at temperatures above the order. of- 400 F. The loss of lubricity is more aggravated, of course, at the highenloads. There is. a lea andaem erature for each lubricant at which its lubricity. lost. With the continued development .of power plants such as internal combustion engines and gas turbine engines and other equipment which operate at ,temperaturesof the order of 700 1'11 and higher, the .for lubricants and hydraulic fluids which will retain desirable qualities at suchtemperatures quite apparent. An object ofthi invention,'therefore, is to provide a material of the fluid organopolysiloxane type which has desirable lubricating qualities at temperatures of the order of 700 F. and higher.

Briefly stated, my invention comprises the hydrolysis and condensation product of organosilanes, for example, those containing chlorophenyl groups and alkyl groups, in combination with tin halide and the process of such combination.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description.

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As pointed out above, the hydrolysis of the monomeric chlorosilanes containing phenyl groups or mixtures thereof with alkyl chlorosilanes is very readily carried out by adding to the mixture of silanes and water an acidic material which will effect hydrolysis such as hydrochloric acid, sulphuric acid, phosphoric acid, etc. As a typical mixture of silanes, I use from about 5 to 25 parts, by weight, of tetrachlorophenyltrichlorosilane, 55 to 92 parts, by weight, of dimethyldichlorosilane, and 3 to 20 parts, by weight, of trimethylchlorosilane along with 100 to 600 parts of water. The amount of water is not critical within the above proportions, it being necessary. only that all the silicon-bonded hydrolyzable groups in the silanes be hydrolyzed.

The following is given as a typical example of the preparation of the above organopolysiloxanes, all parts being by weight. Tetrachlorophenyltrichlorosilane in the amount of 8.5 parts, 845 parts of dimethyldichlorosilane and 7 parts of trimethylchlorosilane were addedto about 300 parts of water. After hydrolysis the water layer is removed and the fluid treated with about 3 parts of an acid such as sulphuric, hydrochloric, phosphoric and the like and heating for a short period of time with stirring. The acid was then removed and the resulting siloxane neutralized as with sodium carbonate and filtered. The

fluid is then devolatili zed to remove all low boilers with boiling points below about 5 mm. at 250 F.

Keeping in mind that the hydrolysis products described above lose their lubricity at about 400 F. for all practical purposes at higher loads, there was sought a material which would stabilize the hydrolysis product. it was unexpectedly found that tin chloride in the hydrated or unhydrated state added to the material in proper amounts produces a lubricant which is superior in its performance at temperatures of the order of 700 F. The tin chloride, calculated as the anhydrous compound, is added to the organopolysiloxane in amounts ranging, by weight, from one percent to ten percent based on the weight of the organopolysiloxane; Preferably, I use from three percent to six percent, by weight, of tin chloride. The organopolysiloxane is very simply stabilized with the tin chloride; the latter being merely added to the organopolysiloxane and the mixture gradually heated to a temperature of about 460 F. at which point the fluid becomes crystal clear. During the heating period any hydrochloric acid generated is driven off, as well as any stannic chloride which is not hydrolyzed. The mixture is next heated to about 750 F. with no evidence of the usual degradation products generally associated with oxidation of organopolysiloxane. Finally, the heated mixture is stripped under vacuum to about 600 F. and filtered. As typical of the tin chloride addition, there was added to the organopolysiloxane five percent, by weight, of tin chloride, the mixture being heated to a temperature of 460 F. At this point, the fluid became clear. The mixture was then heated to 750 F. and then the heated mixture was stripped under vacuum to about 600 F. and

The apparatus used for testing the lubricating qualities of the tin chloride stabilized organopolysiloxane is the so-called Shell Four Ball Wear Tester. This testing device consists essentially of three steel balls, each about one-half inch in diameter, clamped securely in nonrotating fashion in a cup with a fourth ball mounted in a rotatable chuck and adapted to spin in the cavity formed by the three adjacent balls. A loading arm is utilized to force the cup containing the balls against the chuck, the load being varied in any manner desired. Provision is made for holding the lubricant to be tested in the cup containing the balls so that the latter are continually immersed in the lubricant. In testing a lubricant, the apparatus is heated to the temperature desired and the chuck and top ball rotated for a given period of time at a particular number of revolutions per minute under a fixed load. After the test run is completed, the lower or fixed balls are examined with a microscope and the size of the scar worn in them by the upper rotating ball noted and taken as a measure of the comparative lubricating quality under the particular set of conditions. The average diameter of the generally circular scar is used.

Shown in Table I below is a comparison between the organopolysiloxane described above in so far as its lubricating qualities are concerned, as tested on the four ball tester, with the same material to which has been added five percent, by weight, of stannic chloride as described above. The time for each test run was two hours with the rotating ball having a speed of 600 revolutions per minute.

Table I Sear lmrn.) Scar (mm.) Load Temperature (Untreated (Treated F.) Organopoly- Organopolysiloxane) siloxane) From the above it will be apparent that even at the lower temperatures such as 212 F. and 400 F., there is a substantial improvement in the lubricity of the stannic chloride treated material under a load of forty kilograms. At a temperature of 700 F. the treated material shows a substantial improvement over the untreated product even at four and ten kilogram loads and the improvement is all the more pronounced at forty kilograms when the wear scar produced with the treated material is less than one-half that for the untreated material. It will be noted that the performance of the improved lubricant at 700 F. is comparable to that of the untreated material at 212 F. or about 500 P. less.

Following the procedure used with stannic chloride, five percent by weight of stannous chloride was added to the organopolysiloxane described. The resultant product readily supported a 40 kilogram load at 250 F. Furthermore, a forty kilogram load could be carried to about 500 F. without excessive friction, some 300 F. higher than with the base material alone. Using the same Shell Four Ball Wear Tester procedure as above it was found that at 400 F. with a forty kilogram load, the wear scar was 0.8 mm. as compared with a scar of 1.7 mm. for the organopolysiloxane alone. At 500 F. the wear scar was only 1.2 mm. as compared to 2.4 mm. for the untreated lubricant.

It will be understood, of course, that other concentrations of the additives described above may be employed without departing from the spirit and scope of my invention. It will also be apparent that other organopolysiloxane fluids, including those in the reference patents, can be used with the additives to improve their high temperature lubricating characteristics operation at high temperatures and the method of making such lubricants.

These lubricants are characterized. among other things, by the fact that they retain their desirable lubricity at temperatures of the order of 700 F. under high loads.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A lubricating oil consisting of the residue obtained by vacuum stripping at temperatures of about 600 F. the product obtained by heating at a temperature of from 460 F. to 750 F. a mixture of (l) the fluid hydrolysis and condensation product of chlorophenylchlorosilanes and methylchlorosilanes and (2) from 1 to 10 percent of tin chloride, based on the weight of (1).

2. A lubricating oil consisting of the residue obtained by Vacuum stripping at temperatures of about 600 F. the product obtained by heating at a temperature of from 460 F. to 750 F. a mixture of (1) the fluid cohydrolysis and condensation product of, by weight, from about 5 to 25 parts of tetrachlorophenyltrichlorosilane, 55 to 92 parts of dimethyldichlorosilane and 3 to 20 parts of trimethylchlorosilane and (2) from 1 to 10 per cent of tin chloride based on the weight of (l).

. 3. A lubricating oil consisting of the residue obtained by vacuum stripping at temperatures of about 600 F. the product obtained by heating at a temperature of from 460 F. to 750 F. a mixture of (1) the fluid cohydrolysis and condensation product of, by weight, 8.5 parts of tetrachlorophenyltrichlorosilane, 84.5 parts of dimethyldichlorosilane and 7 parts of trimethylchlorosilane and (2) 5 percent tin chloride based on the weight of (1).

4. The process of preparing a lubricating oil which comprises adding to the fluid cohydrolysis and condensation product of, by weight, from 5 to 25 parts tetrachlorophenyltrichlorosilane, 55 to 92 parts dimethyldichlorosilane and 3 to 20 parts trimethylchlorosilane, from 1 to 10 per cent tin chloride based upon the weight of the cohydrolysis and condensation product, and heating the resulting mixture at temperature of from 460 F. to 750 F. and vacuum stripping the resulting reaction product at temperatures of about 600 F.

V 5. The process of preparing a lubricating oil'which comprises reacting at temperatures in the range of from 460 F. to 750 F., (1) the fluid cohydrolysis and condensation product of, by weight, 8.5 parts tetrachlorophenyltrichlorosilane, 84.5parts dimethyldichlorosilane and 7 parts trimethylchlorosilane, with (2) from 1 to 10 percent, by weight, of tin chloride based on the weight of the cohydrolysis and condensation product of (l) and vacuum stripping the resulting reaction product'at temperatures of about 600 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,567 Elliott July 20, 1948 2.465,296 Swiss Mar. 22. 1949 2,742,368 Rossiter Apr. 17, 1956 2,757,152 Solomon July 31, 1956 relied on. 3 

1. A LUBRICATING OIL CONSISTING OF THE RESIDUE OBTAINED BY VACUUM STRIPPING AT TEMPERATURES OF ABOUT 600* F. THE PRODUCT OBTAINED BY HEATING AT A TEMPERATURE OF FROM 460* F. TO 750* F. A MIXTURE OF (1) THE FLUID HYDROLYSIS AND CONDENSATION PRODUCT OF CHLOROPHENYLCHLOROSILANES AND METHYLCHLOROSILANES AND (2) FROM 1 TO 10 PERCENT OF TIN CHLORIDE, BASED ON THE WEIGHT OF (1).
 4. THE PROCESS OF PREPARING A LUBRICATING OIL WHICH COMPRISES ADDING TO THE FLUID COHYDROLYSIS AND CONDENSATION PRODUCT OF, BY WEIGHT, FROM 5 TO 25 PARTS TETRACHLOROPHENYLTRICHLOROSILANE, 55 TO 92 PARTS DIMETHYLDICHLOROSILANE AND 3 TO 20 PARTS TRIMETHYLCHLOROSILANE, FROM 1 TO 10 PERCENT TIN CHLORIDE BASED UPON THE WEIGHT OF THE COHYDROLYSIS AND CONDENSATION PRODUCT, AND HEATING THE RESULTING MIXTURE AT TEMPERATURE OF FROM 460* F. TO 750* F. AND VACUUM STRIPPING THE RESULTING REACTION PRODUCT AT TEMPERATURES OF ABOUT 600* F. 